Method for producing abrasive grains and the composite abrasive grains produced by same

Abstract

The present invention relates to a method for producing abrasive grains. According to the invention the method is characterised by the steps of manufacturing a polycrystalline body comprising diamond particles in a matrix of silicon carbide and silicon, or alternatively metal-silicon-carbon or boron-silicon-carbon phases, and crushing the polycrystalline body into grains. The invention also relates to abrasive grains produced by the method.

What is claimed is:  
     
       1. A low pressure method for producing abrasive grains comprising the steps of forming a work piece from diamond particles, heating the work piece and controlling the heating temperature and heating time so that graphite is created by graphitization of diamond particles during the heat treatment of the work piece in an amount of 1-50 wt-% of the amount of diamond, thereby creating an intermediate body, infiltrating silicon or silicon alloy into the intermediate body, thereby creating a polycrystalline body, and thereafter crushing the polycrystalline body into grains. 
     
     
       2. The method according to claim  1 , wherein silicon alloy is infiltrated into the intermediate body, the alloy comprising at least one metal selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Co, Ni, Cu, Ag and Al, and the elements B and Ge. 
     
     
       3. The method according to claim  2 , wherein the silicon alloy contains Ti, Zr, or Hf in an amount of less than 50 wt-%. 
     
     
       4. The method according to claim  2 , wherein the silicon alloy contains V, Nb, or Ta in an amount of less than 20 wt-%. 
     
     
       5. The method according to claim  2 , wherein the silicon alloy contains Cr and Re in an amount of less than 45 wt-%. 
     
     
       6. The method according to claim  2 , wherein the silicon alloy contains Mo and W in an amount of less than 10 wt-%. 
     
     
       7. The method according to claim  1 , wherein the polycrystalline body is crushed into grains having a size of at least 40 μm. 
     
     
       8. The method according to claim  1 , wherein the work piece is formed of diamond particles having a size of 3-500 μm. 
     
     
       9. The method according to claim  1 , wherein the graphite created by graphitization is 6-30 wt-% of the amount of diamond. 
     
     
       10. The method according to claim  8 , wherein the heating temperature during graphitization is lower than 1700° C. 
     
     
       11. The method according to claim  1  wherein the heating temperature and heating time needed for graphitization is empirically determined for the heating equipment used. 
     
     
       12. The method according to claim  10 , wherein the work piece has a porosity of 25-60 vol.-%. 
     
     
       13. The method according to claim  9 , wherein carbon is deposited in the work piece by exposing the work piece to a gaseous hydrocarbon or hydrocarbons at a temperature exceeding the decomposition temperature for the hydrocarbon or hydrocarbons. 
     
     
       14. The method according to claim  13 , wherein graphitization of the diamond particles in the work piece is done before the work piece is exposed to a gaseous hydrocarbon or hydrocarbons at a temperature exceeding the decomposition temperature for the hydrocarbon or hydrocarbons. 
     
     
       15. The method according to claim  9 , wherein the work piece is formed from a homogeneous mixture of diamond particles of different sizes. 
     
     
       16. The method according to claim  9 , wherein the work piece is formed in a mould and taken out of the mould before the steps of graphitization and infiltration of silicon or silicon alloy takes place. 
     
     
       17. The method according to claim  13 , wherein the polycrystalline body is crushed into grains having a size of at least 40 μm. 
     
     
       18. The method according to claim  1 , wherein the work piece has a porosity of 25-60 vol.-%. 
     
     
       19. The method according to claim  1 , wherein carbon is deposited in the work piece by exposing the work piece to a gaseous hydrocarbon or hydrocarbons at a temperature exceeding the decomposition temperature for the hydrocarbon or hydrocarbons. 
     
     
       20. The method according to claim  1 , wherein the work piece is formed from a homogeneous mixture of diamond particles of different sizes. 
     
     
       21. The method according to claim  1 , wherein the work piece is formed in a mould and taken out of the mould before the steps of graphitization and infiltration of silicon or silicon alloy takes place. 
     
     
       22. The method according to claim  1 , wherein the heating temperature during graphitization is lower than 1700° C.